1. Field of Invention
The present invention relates to a bucket for use in a swinging bucket centrifuge rotor.
2. Description of Prior Art
Swinging bucket rotors are well known in the centrifuge art. In the particular class of very high speed (i.e., "ultra"-class) rotor, the rotor usually comprises a rotor body having an array of cavities located on the undersurface thereof. These cavities are adapted to receive a bucket which when installed hangs from the undersurface of the rotor body. When the rotor is accelerated to high speed the bucket swings from its rest position to a horizontal position, usually with some surface of the bucket coming to rest against a support surface on the underside of the body. This support surface is contoured to receive the bucket, thus transferring some of the load from the bucket hanger to the rotor body. U.S. Pat. No. 3,997,105 (Hayden et al.) is believed a representative example of such a rotor construction. Rotors of this type usually incorporate a spring mechanism in the hanger that allows a pin on the bucket to deflect when the bucket rotates to the horizontal position. This deflection allows the bucket to rest against the support surface of the rotor body.
This traditional type of swinging bucket rotor can sometimes cause difficulties for the clinician. Since the bucket hangs from the undersurface of the body the clinician must reach under the rotor to insert the bucket onto the rotor. This action is rendered even more difficult if the rotor is mounted to on the shaft installed in a centrifuge instrument. It is not uncommon for a bucket to be improperly installed. During operation improper installation of a bucket can cause damage to the rotor and/or, the instrument, or worse, a rotor disruption.
A different type of swinging bucket rotor developed to improve the bucket installation is disclosed in U.S. Pat. No. 3,997,105 (Chulay et al.). This type of swinging bucket rotor is known as a "top loader", owing to the fact that the buckets are installed from the top, usually by dropping onto a pin or a hanger.
One problem with both the traditional and the "top-loader" rotor is the fact that, when the bucket is in the horizontal position, the support surface on the rotor body typically only supports the portion of the bucket lying above a generally horizontal reference plane. Due to unequal support a large bending moment is applied to the rotor body support surface. The rotor body must thus be designed to accommodate this load, resulting in considerably larger and more expensive rotor.
U.S. Pat. No. 4,585,434 (Cole et al.) discloses a rotor in which the bottom surface of the bucket acts as the support surface, with the bucket resting on the structure that is usually considered the rotor windshield. However the requirement of a windshield also adds size and cost to the rotor.
In view of the foregoing it is believed advantageous to provide a top loading swinging bucket rotor that provides support for both the portion of the bucket that lies both above and below a predetermined plane, thus reducing the bending moment applied to the rotor body.